I actually disagree (but this is clearly going to end up as a discussion for another thread!), because to a monster there is no difference between 1 HP and 30 HP. A PC who is up and fighting is one that can be targeted and could target them. I would target a 1 HP PC - but I would not actively have a monster attack a PC who was unconscious. I would regard healing a PC to 1 HP with high damage lurkers around as tactical stupidity and take advantage of it accordingly. I wouldn't regard someone who gets knocked unconscious as a free for all. For the record, I also sometimes ignore PCs who are stunned and dominated too. If you can't act, then I am not going to pay you attention and will attack something else - unless there is good reason to attack the stunned PC (the parties bloodied leader for example).